A known autostereoscopic display device comprises a two dimensional emissive liquid crystal display panel having a row and column array of display pixels acting as an image forming means to produce a display. An array of elongate lenses extending parallel to one another overlies the display pixel array and acts as a view forming means. These are known as “lenticular lenses”. Outputs from the display pixels are projected through these lenticular lenses, which function to modify the directions of the outputs.
The lenticular lenses are provided as a sheet of lens elements, each of which comprises an elongate semi-cylindrical lens element. The lenticular lenses extend in the column direction of the display panel, with each lenticular lens overlying a respective group of two or more adjacent columns of display pixels.
Each lenticular lens can be associated with two columns of display pixels to enable a user to observe a single stereoscopic image. Instead, each lenticular lens can be associated with a group of three or more adjacent display pixels in the row direction. Corresponding columns of display pixels in each group are arranged appropriately to provide a vertical slice from a respective two dimensional sub-image. As a user's head is moved from left to right a series of successive, different, stereoscopic views are observed creating, for example, a look-around impression.
The above described autostereoscopic display device produces a display having good levels of brightness. However, one problem associated with the device is that the views projected by the lenticular sheet are separated by dark zones caused by “imaging” of the non-emitting black matrix which typically defines the display pixel array. These dark zones are readily observed by a user as brightness non-uniformities in the form of dark vertical bands spaced across the display. The bands move across the display as the user moves from left to right and the pitch of the bands changes as the user moves towards or away from the display. Another problem is that the vertical lens result in a much greater reduction in resolution in the horizontal direction than in the vertical direction.
Both of these issues can be at least partly addressed by the well-known technique of slanting the lenticular lenses at an acute angle relative to the column direction of the display pixel array. The use of slanted angles lenses is thus recognised as an essential feature to produce different views with near constant brightness, and a good RGB distribution behind the lenses.
Traditionally, display panels are based on a matrix of pixels that are square in shape. In order to generate images in colour, the pixels are divided into sub-pixels. Traditionally, each pixel is divided into 3 sub-pixels, transmitting or emitting red (R), green (G) and blue (B) light, respectively. Sub-pixels of equal colour are typically arranged in columns.
WO2010/070564 discloses an arrangement in which the lens pitch and lens slant are selected in such a way as to provide an improved pixel layout in the views created by the lenticular array, in terms of spacing of colour sub-pixels, and uniformity of colour density. This case relates to the arrangement of the grid of pixels forming the 3D image, rather than the individual pixels.
The invention concerns the shape of the individual pixels forming the 3D image.
WO 2010/070564 discloses an autostereoscopic display with slanted lenticular lenses wherein a particular lens pitch is selected to achieve a uniform and regular distribution of 3D pixels.